1. Field of Invention
The present invention relates to a material hardness measuring device, and more particularly to a hardness tester, which allows the user to precisely measure the hardness of the material having a limited testing surface thereof.
2. Description of Related Arts
Hand-operated portable hardness meters are already known wherein a conventional hardness meter generally comprises a supporting frame having a flat supporting platform and an actuating gun comprising a driving pin slidably to align with the supporting platform in such a manner that when the testing material is positioned between the supporting platform and the driving pin, a penetrating force of the driving pin is exerted on the testing material so as to determine the hardness of the testing material through the penetrating force. Accordingly, the penetrating force includes a major loading force and a minor loading force wherein the result of the hardness test is determined by the depth of the indention on the testing material with respect to the minor loading force. However, such conventional hardness meter has several drawbacks.
In order to align the testing material between the supporting platform and the driving pin to test the hardness of the testing material, the testing material must provide a flat testing surface for the driving pin to penetrate thereon and a flat supporting surface to bias against the supporting platform. Accordingly, the testing surface and the supporting surface of the testing material must be flat and parallel with each other. Therefore, the testing material having an irregular shaped cannot be tested by such convention hardness meter. Otherwise, the test result of the hardness of the testing material will not accurate due to the uneven testing surface or the uneven supporting surface of the testing material.
Moreover, in order to measure the hardness of the testing material, the actuating gun generally comprises a force sensor angularly detect a linear displacement of the driving pin for determining the penetrating force of the driving pin, such that the force sensor is arranged to read the penetrating force of the driving pin by converting the linear displacement of the driving pin into an angular movement. In other words, the linear displacement of the driving pin is detected and converted to an angular displacement through a L-shaped measuring arm of the force sensor. Therefore, the test result may not precise due to the mechanical deviation of the force sensor.
Alternatively, the measurement device is arranged to read the penetrating force of the driving pin through a compression spring to convert the linear displacement of the driving pin by means of the spring compression force. Accordingly, the penetrating force of the driving pin is converted to the spring compression force by determining the spring coefficient. However, it is known that the compression spring will be deteriorated after a period of time. In other words, both conventional measurement devices of the hardness meter cannot precisely determine the hardness of the testing material due to the mechanical deviation.